Although protective vaccination strategies have been developed against many infectious diseases of viral origin, a vaccine with broad activity against HIV-1 has remained elusive for two decades. Cell-mediated immunity has been implicated in (i) modulation of HIV-1 replication, (ii) protraction of disease progression, and (iii) protection against infection, arguing their importance as components of a successful immunization strategy. Dendritic cells (DC) can present antigens via MHC class I and II pathways and are central to the development of cell-mediated immune responses. Thus, DC-based vaccines are currently being developed as agents to elicit strong, antigen-specific T cell responses, but these protocols usually require ex vivo genetic modification of DCs, followed by re-infusion back into an autologous or MHC-matched host where they mature, migrate to lymph nodes, and present the candidate antigen to CD4 and/or CD8 T cells to elicit antigen-specific responses. Although the ex vivo genetic manipulation approach has been useful in establishing proof-of-concept in an experimental setting, it is not practical for the development of prophylactic vaccines to be used in the field. If transduction of the DCs could be accomplished in situ, the broad use of DC-targeted vaccines as prophylactic agents would be more feasible. However, a critical component of in situ transduction is efficient targeting of the vector to DCs without perturbation of DC function. To this end, we have generated an adenovirus (Ad) vector system that specifically targets DCs via the CD40 receptor and have shown that the CD40-targeted Ad efficiently transduces DCs in vitro without interfering with DC function. A potential limitation of in situ transduction is that sufficient numbers of DC cells must be at the vaccination site to achieve effective immunization. Therefore, we propose to recruit DCs into subcutaneous locales prior to CD40-targeted vaccination by using a novel technology, chemoattractant-releasing polymer rods. In this proposal, we will evaluate the potency of CD40-targeted Ad vectors that express HIV-1 antigens in murine in vitro and in situ vaccination models that incorporate chemoattractant-releasing polymers. Initially, we will optimize the parameters of in situ DC recruitment and determine the degree to which this contributes to the efficiency of in situ CD40-targeted transduction. Next, antigen-specific CD4 and CD8 T cell responses will be compared following immunization with untargeted and CD40-targeted Ad vectors in the presence or absence of DC recruitment. Our hypothesis is that the CD40-targeted Ad will optimally transduce DCs following subcutaneous recruitment to the immunization locale, resulting in the induction of robust T cell immunity. The ability to achieve targeted in situ immunization of DCs followed by the induction of robust antigen-specific T cell immunity will be a milestone in HIV-1 vaccine development. The success of this study will be the impetus for future in vivo studies in non-human primate models to show protective immunity and human clinical trials for populations at high risk of HIV-1 infection.